thanks to both poster, the first confirmed what I thought, the second predicted the understandable confusion of the very friendly train guard who undertook research and used her discretion, such that we could both find the answer another time. Well done to all. Many thanks.
All the guard has to do is enter the origin and destination, and select the ticket type and their machine should tell them the restriction.
I know it's not easy for the general public to find out and PhilipW's post is entirely valid,
but surely a
guard should easily be able to find this out?
Or was her machine not working, in which case she has little choice but to accept all tickets and advise anyone without a ticket to buy at their destination?
The general public are not allowed to see a list of the restrictions without paying £9+VAT+P&P for a CD containing about 15MB of data in the form of the Avantix Traveller NFM software. Instead, we are supposed to ask staff for the restriction (they are meant to tell us when we buy our tickets but some are so long that never happens). Or you can ask here!

Or, alternatively, it is available on file sharing websites for nothing. We don't permit such links to file sharing sites however it can be ordered legally from
TSO.